This invention relates to cellular electrical stimulation in general, for animals and other life forms, as fish and plants, including humans, and neuron, heart muscle, other muscles and organs electrical stimulation in particular, including in particular brain, spine and heart. It also relates to electrical measurements of cells in general, and of neurons in particular.
It is well established in the field of neurological science that neurons work by propagating electrical signals. This is know to be true whether the neurons are transmitting an order from the brain or other initiating point to another body part, as an order to move the leg forward, which is a complex set of commands, or for a heart beat, that is simpler than a leg movement, delivered to the sinus, or on the other direction, transmitting a sensation from some body part to the central nervous system, as temperature or pain somewhere, or simply thinking, as pondering about the meaning of this very patent disclosure, which is an electrical activity that is completely inside the brain.
It turns out that the brain is divided in parts dedicated to special tasks that are in relative position to each other in the same way in all animals of a particular species and even approximately the same across species. These parts are three dimensional but are called areas by the neurologists. Accordingly, the areas that are used to detect and process vision are located very much the same way in all H. sapiens, with little difference to chimpanzees and more differences to cats, which is a consequence of biological speciation and relatedness. The internal parts of an animal are variable in size from individual to individual as much as the external parts are, as size of nose, mouth or hand, but as much as in humans the nose is always above the mouth, each specialized part of the brain has a slightly different absolute size in each individual, but is relatively positioned to each other in the same way in all humans. These brain parts are known by neurologists as areas, as Broca area, Wernicke area, etc. It is also known that constant use can enlarge areas that are requested constantly, as shown by the work with London cab drivers. So, what the neurologists call area is really a volume in standard parlance, the place that contains all the neurons involved in a part or in the totality of some particular neurological activity occurs. So, Broca area, as the neurologists call it, is really the Broca volume, as a lay person would, because it is a 3-dimensional arrangement, etc. In the disclosure we most often use the word “volume” because it is a better descriptor, but in established uses, as named regions of the brain, as the Broca area, we use “area”.
The brain of Homo sapiens is now all mapped, that is, the function of all areas is known to the neurologists. Accordingly, the Broca area is responsible for speech and its position is known, the Wernicke area is responsible for hearing, also at a known location, and so forth, and their position in the brain is well known to the neurologists. Yet, though their relative position is the same, their absolute position with respect to some external mark is not the same in all humans, among other reasons because humans come in different sizes, but also because even two humans of the same height have noses, hands, hearts, livers and Broca and Wernicke areas of not exactly the same size, and even the same exact shape. Eric R. Kandel (Eric R. Kandel et al., “Principles of Neuroscience” (2000), several editions.) gives a good overview of the current state of the art from the academic point-of-view.
Accordingly, two fields have been developing: neurological research and correction of neurological disorders. These have advanced to the point that it is now common, ordinary, daily practice, to measure electrical signals in neurons, and also to add electrical stimulation to them to change their actions. The former, neuron measurements, are only rarely done in humans, and done in experimental animals under close monitored conditions, after receiving approval of some internal reviewing board that oversees animal research. Naturally that in mammals, experiments are under closer control than in fish, and more loosely control on insects and the like, because few humans care much about the Drosophila melanogaster, a feeling that is reciprocated, the inventors believe.
The latter, electrical stimulation, is a common surgery practiced today, mostly to control Parkinson's disease, but in smaller numbers for other neurological malfunctions too, as epilepsy, and other disorders. Electrical stimulation is also done for pain control and for organ stimulation (including increasing and decreasing organ activity), as for appetite control, bladder control and the like.
We introduce here an important terminology, crucial to our invention: electrode. It means the ending portion of the stimulating device, from which electrical current is injected into the cells, as neurons, muscle, etc. Also known as pad. Accordingly, electrodes for both neuron measurements and stimulation have been developed and are commercially manufactured by a number of companies. Electrical neuron measurements are not widely known to be done in the lab, though they are, but electrical stimulation is widely known in its incarnation as heart pacemakers, that are designed to stimulate the heart muscle by adding an electrical pulse to the one delivered at the sinus node. A pacemaker is used when the electrical pulses to the sinus node becomes defective.
Therefore for both neuron measurements and for neuron stimulation, there exists a need to reach a number of neurons, the position of which is difficult to determine with respect to some external feature, as the top of the head or the mammary gland, from which to go to the hypothalamus in the brain from a 1 cm. hole on top of the head, or the sinus node in the heart, from a vein in the clavicle. This is so because, though the relative position of the neurons and cells responsible for each task is generally the same in animals of the same species, the absolute distances is not the same from animal to animal. It follows that it is very difficult for a neurologist to know exactly where the inserted electrode is, whether he/she is interested in making an electric measurement in the brain of a laboratory animal, or in implanting an electrode on a Homo sapiens to control Parkinson's disease. To counter this difficulty, electrode arrays have been introduced both for measurements and stimulation. For measurements there exists arrays composed of several dozen electrodes separated by 50, 100, 250 micrometers, and for neuron excitation, generally larger distances, but details depend on the particular situation. Neither of these have been able to make use of a very large number of electrodes because of the difficulty in passing a large number of wires to connect them to the outside world. Our inventions U.S. patent pending application Ser. No. 12/586,763, filing date Sep. 28, 2009 and application Ser. No. 12/586,562, filing date Sep. 24, 2009 which are incorporated herein by reference in its entirety, as well as the Provisional Patent Application associated with each of these, disclosed methods and means to connect a much larger number of electrodes, in one case to measure, on the other case to stimulate. With the addressing method disclosed in these patents, instead of having n wires to activate each electrode separately, the same n wires used as an address bus can generate 2 power n (2-super-n) addresses, which in turn can select that many electrodes. Bus here is used in the digital electronics meaning: a set of wires grouped according to its function. For example, the address bus is the set of wires which carries the address value for something, the data bus is the set of wires which carries the data, or numerical value for some information. For example, one commonly used brain stimulator marketed by Medtronic uses 4 connecting wires to stimulate any one of a set of 4 electrodes at the end of the lead. Using the same 4 wires as an address bus, there is the possibility of selecting 2-super-4=16 separate electrodes, which allows for a much larger selection of points to start electrical stimulation. Yet if these inventions substantially decreased the number of wires to make the necessary connections to a large number of electrodes, it is possible to decrease the number of wires even further, which is very important in an implanted device which must be as little intrusive as possible to make.